Canine ehrlichiosis is a lethal disease caused by Ehrlichia canis (E. canis), a blood-borne intracellular pathogen, and infects all breeds of dogs at any growth phase. Canine ehrlichiosis is transmitted primarily by the brown dog tick, Rhipicephalus sanguineous, which is believed to be the primary reservoir for the disease. Canine ehrlichiosis is a potentially lethal disease that is endemic in the United States and occurs worldwide. Symptoms commonly progress from an acute to chronic disease state depending on the strain of the organism and immune status of the host. In acute cases, symptoms include mucopurulent ocular and nasal discharge, dehydration, reticuloendothelial hyperplasia, fever, generalized lymphadenopathy, splenomegaly and thrombocytopenia. In chronic cases, variable signs of anorexia, depression, loss of stamina, stiffness and reluctance to walk, edema of the limbs or scrotum, and coughing or dyspnea may occur.
There is currently no vaccine available for the effective treatment or prevention of canine ehrlichiosis. The common treatment for all forms of ehrlichiosis is administration of an antibiotic, such as tetracycline, for a minimum of 2 weeks for acute cases, or 1-2 months in chronic cases. In chronic cases, the hemotologic abnormalities may persist for 3-6 months, or for a lifetime. Supportive therapy may be necessary to combat wasting and specific organ dysfunction. Clearly, effective prevention of the disease would be preferred over a post-infection antibiotic regime.
Therefore, it is an object of this invention to provide a safe and effective vaccine composition useful for the induction of protective immunity against canine ehrlichiosis in dogs.
It is another object of this invention to provide a method for the prevention or amelioration of canine ehrlichiosis in dogs.
It is a further object of this invention to provide a method for the induction of clinical canine ehrlichiosis in a test animal. Said method is useful for the evaluation and study of host defenses and pathogenic mechanisms, and for the improved development of vaccines against ehrlichiosis.
It is a feature of this invention that the vaccine composition can protect dogs against multiple strains of E. canis originating in a variety of geographic regions.
It is another feature of this invention that effective protective immunity against canine ehrlichiosis may be imparted to dogs of any age.
Further objects and features of the invention will become apparent from the detailed description set forth hereinbelow.